This invention relates generally to a fluid jetting apparatus. In a particular aspect, the present invention relates to a self-rotating jetting nozzle whose speed of rotation is restricted by eddy current damping.
In industrial cleaning (such as for removing rust, scale, etc. off of metal surfaces in heat exchanger tubes and in cracking towers, for example), various sizes of rotating nozzles can be used to apply streams of fluid to the surfaces to be cleaned. These nozzles typically rotate in response to one or more streams of fluid jetting from eccentric ports in the nozzles. The force of such a fluid stream not only rotates a nozzle, but also scours the impacted surface.
Self-destructive forces can occur in these nozzles if the speed of a rotating member is allowed to increase unchecked. Typical large nozzles (e.g., 3 inches in diameter or larger) have mechanical braking systems or viscous fluid braking systems to stop or retard the rotating members from rotating too fast. Typical self-rotating small nozzles of which I am aware, on the other hand, do not have any braking mechanism; therefore, these small nozzles can accelerate until such speeds are reached that they begin to self-destruct through friction, heat and centrifugal force. This is detrimental not only to the nozzle itself, but, also to the cleaning process and possibly to the object being cleaned. A catastrophic failure of this type can also be hazardous to personnel.
In view of this self-destructive nature, there is the need for some type of small nozzle whose speed can be limited or retarded to keep it from rotating at a destructive speed. The mechanism by which this is achieved must accommodate the small size of the nozzle itself as well as the small or tight environments where such a nozzle is to be used.